1. Field of the Invention
The present invention is related to a backlight module, and more particularly, to a backlight module able to provide a liquid crystal display with a light source generator having a high color rendering property.
2. Description of the Prior Art
Backlight modules are one of the major component devices of liquid crystal display (LCD) products, and have been widely applied to digital cameras, mobile phones, personal digital assistants (PDAs), computer monitors, and flat TVs at present. Generally, a backlight module, being mostly installed in the backside of a display panel, includes a light source generator, a light guide plate, and several sorts of light diffusion elements. The light guide plate is one of the light diffusion elements used for diffusing light generated from the light source generator to the display panel for providing homogeneous brightness to the display panel.
Generally, backlight modules may roughly be divided into two categories: direct-underlying backlight modules and edge-lit backlight modules. The design of direct-underlying backlight module is to place the light source generator in the backside of the display panel. Since the holding space is larger, plenty of lamp tubes can be used to enhance the light intensity so that it is widely applied to a display panel requiring higher brightness and larger size. An LCD monitor with a high-brightness requirement or designed for use outdoors, or an LCD TV is suitable for applying the direct-underlying backlight module thereto. Furthermore, the direct-underlying backlight module often adopts a plurality of lamp tubes, such as cold cathode fluorescent lamps (CCFLs) or external electrode fluorescent lamps (EEFLs) as a light source generator. On the other hand, the light source generator of an edge-lit backlight module is placed to the edge of the backlight module to reduce the thickness. This kind of design can fit consumer demand of light, thin, and low-power devices and is mainly applied to portable information products. Taking mobile phone as an example, most LCD modules used are edge-lit backlight modules, and the light source generator is a group of light emitting diodes (LEDs), which have advantages of small size and low power consumption.
Generally, an LCD module requires white light from its light source generator. However, the technique of developing white light LEDs is not mature, so that a conventional LED light source generator uses fluorescent powders with a monochromatic LED (such as a blue LED) to obtain white light. The principle is that the fluorescent powders absorb a part of the blue light produced by the LED chip to emit yellowish-green light, and the remaining blue light is mixed with the yellowish-green light to form white light. Applying the white light produced by the monochromatic LED chip together with the fluorescent powder as the light source generator of the LCD module is well-known. However, a drawback of this method is insufficient color saturation of the LCD module due to a smaller distribution of the color range so that the performance of a small LCD module using an LED as its light source generator is inferior to that of the large LCD monitor having conventional fluorescent lamps. This needs to be improved.